The name Guinea is usually said to have been a corrupt form of the name Ghana, picked up by the Portuguese in the Maghrib. The present writer finds this unacceptable. The name Guinea has been in use both in the Maghrib and in Europe long before Prince Henry's time. For example, on a map dated about 1320 by the Genoese cartographer Giovanni di Carignano, who got his information about Africa from a fellow-countryman in Sijilmas , we find Gunuia, and in the Catalan atlas of 1375 as Ginyia. A passage in Leo (vol. III, 822) points to Guinea having been a corrupt form of Jenne , less famous than Ghana but nevertheless for many centuries famed in the Maghrib as a great market and a seat of learning. The relevant passage reads: "The Kingdom of Ghinea . . . called by the merchants of our nation Gheneoa, by the natural inhabitants thereof Genni and by the Portugals and other people of Europe Ghinea." But it seems more probable that Guinea derives from aguinaou, the Berber for Negro. Marrakech has a gate, built in the twelfth century, called the Bab Aguinaou, the Gate of the Negro (Delafosse, Haut-Sénégal-Niger, II, 277-278). The modern application of the name Guinea to the coast dates only from 1481. In that year the Portuguese built a fort, São Jorge da Mina (modern day Elmina), on the Gold Coast region, and their king, John II, was permitted by the Pope to style himself Lord of Guinea, a title that survived until the recent extinction of the monarchy.
The name "Guinea" was also applied to south coast of West Africa, north of the Gulf of Guinea, which became known as "Upper Guinea", and the west coast of Southern Africa, to the east, which became known as "Lower Guinea". The name "Guinea" is still attached to the names of three countries in Africa: Guinea, Guinea-Bissau, and Equatorial Guinea, as well as New Guinea in Melanesia.
The main river shedding its waters in the gulf is the Niger River.